test(e2e): Cover queue pause and freeze across every switch combination

[manjari25]

Why?

Queue pause is two independent switches, reject new lands and freeze processing. The unit tests cover each in isolation, but nothing yet proves that the switches work together, that a freeze really holds a queue's pipeline, or that a rejection reaches a caller as the right status with the operator's reason.

What?

• Adds e2e tests for all four switch combinations: running, drain (reject only), hold (freeze only) and full pause.
• A frozen request is shown to be held, not merely slow: a request on an unpaused sentinel queue must land first while the frozen one stays accepted.
• A rejected land is checked for FailedPrecondition, and the full-pause test also checks that the operator's reason reaches the caller.
• Compose wiring: the gateway and orchestrator read QUEUE_PAUSE_CONFIG_PATH from a mounted directory, and a dedicated e2e-pause-queue is added. Pausing stays off by default, so the local stack starts as before.
• The tests replace the pause file by rename inside the mounted directory, so a reader sees the old or new contents and never a parti

Test Plan

• bazel test //test/e2e/submitqueue:go_default_test --test_arg=-testify.m=TestQueuePause runs the four pause tests.
• CI

Issue